nuke and particle physics Flashcards
what is an isotope
same number of protons; diff number of neutrons
what nuclear forces act on hadrons
both strong and weak
what is a hadron
subatomic particle made up of quarks
what are the two types of hadrons
baryons and mesons
what are baryons
hadrons made of three quarks
what are mesons
hadrons made of a quark and antiquark
what interaction causes beta decay
weak nuclear force
an alpha particle is fired at a stationary gold nucleus; at one point the alpha is stationary and the gold has velocity; explain what happened
electrostatic repulsion between the particles; momentum conserved due to no external force; so gold has (lower) velocity; KE of alpha particle converted to electric PE
which type of decay produces a normal neutrino
beta plus decay (antineutrino for beta minus)
why are protons and neutrons not fundamental particles
they are made up of quarks
name some leptons
electron; positron; neutrino; antineutrino
what nuclear forces act on leptons
only weak
how did the alpha scattering experiment give evidence for the nuclear model of the atom
most alpha particles went straight through, showing most of the atom is empty space; some were scattered, showing a dense positive nucleus
what is the binding energy of a nucleus
min energy to separate all nucleons
what is mass defect
change in mass due to binding energy (energy change due to forming a nucleus)
why is the mass of a nucleus different from the total mass of its nucleons
energy released to form nucleus from nucleons; E = mc^2, so mass of nucleus is smaller
explain nuclear fusion; refer to the conditions needed
electrostatic repulsion between nuclei; high temperature and pressure required to overcome it; nuclei get close enough for strong force to start acting; overall decrease in mass occurs, releasing energy
why is radioactive decay said to be spontaneous and random
spontaneous - cannot be induced; random - time of next decay cannot be predicted
explain the technique of carbon dating
living things take in C-14; they stop once dead; activity of C-14 is measured in both a dead and living sample; equation used with this data to estimate age
explain why carbon dating has an age limit
activity becomes so low you can’t tell it from the background
what physical properties make nuclear waste dangerous
radioactivity causes ionisation; can be active for a long time
explain induced nuclear fission
a slow moving neutron splits a nucleus into two smaller nuclei + fast moving neutrons; overall decrease in mass occurs, releasing energy
state and explain the purpose of a moderator in a nuclear reactor; include how it works at a microscopic level
moderator slows down neutrons; nuclear fission produces fast moving neutrons; they collide with moderator atoms and pass on their KE; slow moving neutrons can cause more fission (chain reaction)
what are control rods used for in a nuclear reactor
they absorb neutrons
describe the nature of the strong nuclear force
acts between hadrons; short range
two protons fuse together; explain how they are able to remain together
strong nuclear force makes them attract
